1. Field of the Invention
The invention generally relates to methodology for forming a free-standing article, and to the free-standing article thereby formed. In particular, the invention relates to free-standing (Al, Ga, In)N articles, and to methods of forming same by interfacial separation of (Al, Ga, In)N from a base material or layer on which the (Al, Ga, In)N has been grown, to yield the separated (Al, Ga, In)N material as a free-standing body suitable for fabrication of microelectronic or optoelectronic devices.
2. Description of the Related Art
U.S. Pat. No. 5,679,152 describes the production of a free-standing (Al,Ga,In)N single crystal article on an epitaxially-compatible sacrificial template, in which a layer of single crystal (Al,Ga,In)N is deposited on the template, and sacrificial template is removed at or near the growth temperature to leave free-standing (Al,Ga,In)N.
This method produces a low defect density (e.g., <107 defects/cm2) material as a result of the absence of thermal coefficient of expansion (TCE) differences associated with the substrate when a heteroepitaxial substrate material is used for the template, since the template is removed in situ. As a result, the internal stresses incident to the mismatch of TCE that normally accompany the cool-down of heteroepitaxial materials and that cause cracking and morphological defects, are avoided.
The present invention relates to free-standing (Al, Ga, In)N articles, and to formation of same by growth of (Al, Ga, In)N material on a sacrificial template, and interfacial separation of the (Al, Ga, In)N material from the template, to yield device-quality single crystal (Al, Ga, In)N free-standing articles.